July 3, 2018 — Determining the cause of whale deaths is slow and difficult. A vessel strike likely killed the juvenile humpback whale that washed ashore in Jamestown in June 2017, but the determination is not conclusive, according to federal Marine Mammal Health and Stranding Response Program.
It’s common not to know what killed a whale because decomposition, especially of internal organs, happens quickly. Large sea mammals like right whales are too large to bring to a labratory and often have to be towed to shore — trailed by sharks — to perform a thorough examination. A full necropsy may take days to complete and require large equipment such as a backhoe to move a carcass that can weigh up to 150 tons. Scientists must contend with odors, layers of blubber, and offshore conditions.
“If you don’t have the machinery it can take days and days, you may never finish,” said Michael Moore, a veterinarian and whale biologist at the Woods Hole Oceanographic Institution, in an interview with NBC News.
What is known is that whale deaths have spiked in the Atlantic. Currently, the National Oceanic and Atmospheric Administration (NOAA) is monitoring an unusual increase in whale deaths, called unusual mortality events (UME), for three species of whales: minke, humpback, and the North Atlantic right whale.
North Atlantic right whales are highly endangered, with an estimated population of 450 and declining since 2010. If the current trend continues, the species could be extinct in 20 to 25 years, according to researchers.
Vessel collisions and entanglements with fishing gear are the leading causes of whale deaths. Fishing gear snares some 83 percent of North Atlantic right whales at least once in their lives.
The right whale UME began in June 2017 and, so far, 12 of the 19 deaths occurred in the Gulf of St. Lawrence in Canada. Four washed ashore in Massachusetts.